Recently, a surface area of a semiconductor device has been steadily increasing due to high integration and three-dimensional structure of the semiconductor device. In a semiconductor manufacturing process, a so-called loading effect such as a change in thickness of a film formed on a substrate due to an increased surface area of the semiconductor device becomes a serious problem. Thus, a film forming technique for suppressing an influence of the loading effect is required. As a method for coping with such a demand, there is a method of forming a film by alternately supplying process gases onto a substrate.
The method of forming the film by alternately supplying the process gases is effective for suppressing the loading effect. Recently, a substrate having a surface area at least three times of that of a bare substrate may be used. The term “surface area” throughout this specification means the total area of all the outside surfaces of three dimensional shapes (such as patterns) formed on the upper surface of a substrate. The bare substrate refers to a substrate that no pattern is formed thereon. Hereinafter, the substrate whose surface area is at least three times of that of the bare substrate is referred to as a “large surface area substrate”. When a batch processing apparatus such as a substrate processing apparatus configured to load (charge) and process a plurality of large surface area substrates according to the above-mentioned method of forming a film by alternately supplying the process gases, a thickness of a film formed on each of the large surface area substrates may vary depending on the surface area of each of the large surface area substrates and the number of the large surface area substrates loaded in the batch processing apparatus. Therefore, it is difficult to control the thickness of the film formed on each of the large surface area substrates.